Systems which extract hot exhaust air from turbines of an aircraft driving apparatus are generally employed for the control of temperatures in aircraft cabins. This hot air, referred to as driving apparatus tap air, is cooled down to a temperature desired in the aircraft cabin. In the case of aircrafts, whose cabins are divided into different temperature areas or climate zones, a portion of the hot air is cooled down to the lowest temperature of one or more temperature areas. In order to achieve higher temperatures in other temperature areas, a portion of the hot air is branched off before the cooling to the lowest temperature, is cooled to a lesser degree, thus brought to a temperature above the lowest temperature, and mixed with the air that has been cooled to the lowest temperature such that in these temperature areas the desired temperatures are achieved. With such a system, which is also known as the “Trim-Air System”, individually adjustable temperatures can be provided in the different temperature areas of an aircraft cabin.
FIG. 1 illustrates in simplified form such a known system 2 for temperature control in an aircraft cabin 4. System-specific terms of components outlined below are respectively specified in brackets.
The aircraft cabin 4 is divided into two temperature areas 6 and 8 which comprise for example the right and left side, respectively, of the aircraft cabin 4. Each temperature area 6, 8 is in turn divided into individual temperature zones. In FIG. 4 four temperature zones 10 to 16 for the temperature area 6 and for the temperature area 8 four temperature zones 18 to 24 are exemplarily illustrated.
In order to indicate current temperatures prevailing in the temperature zones 10 to 24, temperature sensors 26 to 40 (duct sensors) are used. The temperature sensors 26 to 40 are disposed in end areas (not shown) of air outlet ducts 42 to 56 (ducts), which serve for a supply of air into the temperature areas 6 and 8. Moreover, further temperature sensors (not shown) are disposed in the aircraft cabin 4 itself in order to provide additional information about temperatures in the temperature zones 10 to 24.
In each of the air outlet ducts 42 to 56 is disposed a valve 58 to 72 (trim-air valve). The valves 58 to 72 are controlled depending upon a currently prevailing temperature in a corresponding temperature zone 10 to 24. Signals from the temperature sensors 26 to 40 are processed by a control device 74 (trim-air-system controller) in order to control the valves 58 to 72 such that in the temperature areas 6 to 8 and in the temperature zones 10 to 24, respectively, desired temperatures are achieved and maintained, respectively.
The system 2 obtains heated air via two valves 76 and 78 (trim-air pressure regulating valve). Heated air supplied via the valve 76 is based on hot air from the driving apparatus on one side of the aircraft, while air supply via the valve 78 originates from the driving apparatus on the other side of the aircraft.
The valves 76 and 78 are pneumatically controlled valves, which are pre-adjusted such that relative to the internal pressure in the aircraft cabin 4 and to the internal pressures prevailing in the temperature areas 6 and 8 in the air ducts 80 and 82 (trim-air supply duct) a substantially constant pressure is maintained. The adjustment of the valves 76 and 78 is mechanically realized beforehand and cannot be varied during the flight.
In addition to the positions of the valves 76 and 78, which positions are, variable in normal operation by means of pneumatic control, the valves 76 and 78 can be fully opened if extreme heating power is required to heat the aircraft cabin 4. This is the case, for example, if the aircraft is to be heated rapidly before take off.
Heated air supplied via the valves 76 and 78 is guided via the air ducts 80 and 82 via areas 84 and 86 to the valves 58 to 72. The areas 84 and 86 are comparable to manifold areas, which is why the areas 84 and 86 are also referred to as trim-air manifolds. Downstream from the valves 58 to 72 and upstream from the temperature sensors 26 to 40, heated air supplied via the valves 76 and 78 is mixed with air having a temperature that corresponds with the lowest desired temperature for the temperature zones 10 to 24. The components required for this are not shown in FIG. 1.
The air ducts 80 and 82 can be connected together via a valve 88 (trim-air shut-off valve), which is closed in normal operation. If for example the valve 76 or its air supply fails, valve 88 is opened in order to control, in addition to the temperature area 8, the temperature of the temperature area 6 by way of heated air obtained via valve 78.
Check valves 90 and 92 (trim-air check valve) are disposed in the air ducts 80 and 82 upstream from the areas 84 and 86 and downstream from the valves 76 and 78, respectively. The valves 90 and 92 serve as blocking means in order to prevent reflux of air from the valves 76 and 78. Should valve 88 be opened in the event of a malfunction, for example, of the valve 76, the valve 90 prevents heated air supplied via valve 78 from reaching valve 76 and is consequently available for temperature control in the aircraft cabin 4.
In view of the design of the system 2 for temperature control in two temperature areas 6,8 shown in FIG. 1, such a design is also referred to as a two-quadrant system. Should one of the valves 58 to 72 malfunction or fail completely it may no longer be possible to accomplish the temperature control in the corresponding temperature zones and potentially in the corresponding temperature area such that the temperatures desired there can be reached and maintained, respectively.
If, for example, valve 58 fails in a substantially fully opened state, it is possible that at least the temperature zone 10 becomes too warm. In case of a failure of the valve 58 in a substantially closed state, an undesirably intense temperature drop in the temperature zone 10 may occur.
In FIG. 1, the components of the trim-air system 2 used for the temperature area 6 represent the first quadrant, while the components serving the temperature area 8 represent the second quadrant.
To avoid this, in the event of a failure of one of the valves 58 to 72, the heated air supply-serving valve 76, 78 of the corresponding quadrant is fully closed. Should for example the valve 58 (partly/fully) fail, the valve 76 is closed. Correspondingly, the valves 60 to 64 and thus also the temperature zones 12 to 16 are no longer supplied with heated air. A control of temperature in the temperature area 6 is then no longer possible.
A supply of the malfunction-free valves 60 to 64 with heated air from the valve 78 by opening the valve 88 is not achievable, because the malfunctioning valve 58 is then also supplied with heated air. It is precisely this, however, that should be avoided.
To avoid a too intense temperature drop or increase in the temperature area 6, the minimum temperature of the air mixed in downstream from the valves 58 to 72 (i.e. the lowest temperature zone temperature) can be increased or lowered. In this case a compromise between temperatures in the temperature areas 6 and 8 must be arrived at to avoid on the one hand passengers in the temperature area 8 from being subjected to too high temperatures and on the other hand passengers in the temperature area 6 from being subjected to too low temperatures.
The object of the present invention is to provide solutions, which provide an improved temperature control in a room, and particularly to solve the problems of the state of the art named above.